Digitally stored information is pervasive and encompasses every facet of everyday life. Increasing amounts of personal, private, confidential or otherwise sensitive information is stored on portable devices. If such devices are lost or stolen, this information is potentially compromised. Approaches to protecting stored information can broadly be classified as physical and cryptographic.
Physical protection involves ensuring that the hardware containing the stored information is physically secure and does not fall into the hands of those who might abuse it. Physical protection is not always practical, especially in the case of portable devices which are subject to loss or theft. Cryptographic protection involves encrypting stored information using one or more secret keys and protecting the security of the keys. Cryptographic protection has been wide employed on storage devices. Many disk drive manufacturers today offer full disk encryption and operating system support for disk encryption has been available for some time. Cryptographic protection relies on a secure key management system. If the key or keys are compromised, protection of the information may be lost.
Prior approaches to data security have focused on physical and cryptographic protection. An independent but related concept is the issue of data deletion. In many cases it is desirable to delete previously stored information. This can be in the case that a storage device is being decommissioned or discarded and/or the data is no longer needed or wanted. Data deletion is also a form of protection in that deleted data is no longer accessible to anyone, including those not authorized to access it. Data deletion approaches can be broadly classified as physical destruction, data overwrite and cryptographic. In the case of physical destruction the hardware containing the information is physically destroyed, rendering access to it impossible. Physical destruction of storage devices is cumbersome and may be unreliable. In the case of data overwrite, new data is written over previously existing data. Data overwrite can be time consuming, especially if conservative approaches to data overwrite are employed, in which data is overwritten multiple times with different patterns. Cryptographic deletion involves encrypting information that is stored and deleting the keys used to store the information. A cryptographic approach to data deletion does not require any physical destruction and can be done quickly without any need to change the data that is stored on the storage device.
Unfortunately existing approaches to data encryption do not provide efficient and convenient methods for data migration, where an encryption system can be applied to an unencrypted data storage device and an encryption policy can be gradually applied. Improved systems and methods for incremental data encryption are needed.